Many props and pieces of decoration in Star Trek were later modified or even
recycled without changes to represent equipment for a different purpose or of
another civilization. Here are quite a
few examples of stationary computers, control consoles and displays. Please note that every statement made here should be taken with a grain of salt.
There is no need to seek for explanations. Certainly we are not
supposed to watch closely enough to notice that the equipment looks all the same
everywhere in the galaxy.

Viewscreens

Engineering displayIn
TNG: "Booby Trap" a device behind Leah and Geordi displays the warp core
status. It has a distinctive rounded edge. In "Star Trek VI: The
Undiscovered Country" a crewmember flees an explosion aboard the Enterprise-A. Note the display in the
middle; it seems that the design for the Enterprise-D's core has traveled backwards in time!

Starfleet & alien viewscreen
The viewscreen of the Enterprise-D's battle bridge (which was no permanent set)
was also used for the Atlec ship in TNG: "The Outrageous Okona", as
well as for Baran's pirate ship in TNG: "Gambit", each time with a few
modifications. The battle bridge itself was rebuilt for TNG: "The Best of
Both Worlds". The viewscreen remained essentially the same though.

Risan & Zalkonian screen The
computer screen seen on Risa in TNG: "Captain's Holiday" later appears
on the Zalkonian ship in TNG: "Transfigurations", albeit in a little
prominent place somewhere in the background.

Ktarian & Romulan viewscreen
The command chair as well as the main screen of the Ktarian ship from TNG:
"The Game" show up on the Romulan warbird in TNG: "Face of the
Enemy". What does it tell us about the state of the empire that the
Romulans need to steal their furniture from minor races? ;-)

Hexagonal wall panel
On the Romulan ship in TOS: "The Enterprise Incident" we can see
elongated hexagonal wall panels beside the doors with something like a button, a
light, and/or a sensor in the center (part of a Romulan style that comprises
several more hexagonal shapes, such as notably the Romulan
emblem). They reappear on the Eymorg homeworld in TOS: "Spock's
Brain".

Tall console
This type of computer consoles appeared on Aldea in TNG: "When the Bough
Breaks", but also as Starfleet equipment in the 23rd century ("Star
Trek V") and in the 24th century (TNG: "Coming of Age", "The
Emissary" and several more TNG episodes).

Custodian consoleThe Custodian console on Aldea from TNG: "When
the Bough Breaks" reappeared in "Star Trek V: The Final Frontier" as a Klingon communications console on Nimbus III.
It was also visible on the Romulan warbird in TNG: "Contagion" and on
the Pakled ship Mondor in TNG: "Samaritan Snare".

Floor/overhead console
The central console in the sensor control room that Worf and Geordi are working on
in TNG: "Lonely Among Us" appeared several more times on TNG. One early re-use is in "The
Outrageous Okona" on the bridge of the Straleb vessel.

Console with octagonal screens
Consoles with octagonal screens appeared in one way or another in the first four Star Trek feature films. They were seen on the aft section of the bridge of the Klingon battlecruiser Amar in "Star Trek: The Motion Picture". Then they
showed up in main engineering in "Star Trek III: The Wrath of Khan". In "Star Trek III: The Search for Spock", only the small octagonal displays were used and seen on the bridge of Kruge's Klingon Bird of Prey. In "Star Trek IV: The Voyage Home" the whole console walls finally appear on the Klingon Bird of Prey.
Note that in "Star Trek II" and "Star Trek "IV" the
console can be seen together with
the same wall piece with holes in it.

Console with levers A
console with untypical (for Trek) mechanical levers can be seen on a the Ferengi
ship in ENT: "Acquisition", but also on a Suliban
ship in ENT: "Shockwave" and on a Xindi-Insectoid vessel in ENT:
"Azati Prime".

Round console
A console of unknown purpose with a round superstructure and large blinking
lights can be seen in the Captain Proton simulation in VOY: "Night", as
well as on the Son'a command ship in "Insurrection", on the Talaxian asteroid in VOY: "Homestead"
and on the
Orpheus station in ENT: "Demons".

The re-used Enterprise-D engineering display
was found by Nathan Koga,
the Defiant viewscreen, "pool table" and more TOS consoles by Michael Minnick. Simon
Allen and unitron6991 spotted the lever consoles and Ron
Ferrara the pyramid console.